Conventionally, a defect in the cranial bone has been repaired by a prosthetic member for cranial bones (cranial bone plate). The cranial bone plate is formed from safety material. Examples of known safety materials include ceramic materials (apatite-based ceramics, alumina ceramics, zirconia ceramics, etc.), metal materials (titanium, titanium alloys, cobalt-chromium alloys, stainless steel, etc.) and polymer materials (polymethyl methacrylate, polyether ether ketone, polyethylene, etc.) (see, for example, Patent Documents 1 and 2).
In particular, ultrahigh molecular weight polyethylene (UHMWPE) has excellent properties, including its light weight, high strength, excellent impact resistance and good formability, and thus UHMWPE is a promising material for the cranial bone plate.